Control of contrast with color developers



55 In such processes, the

l atented Apr. 10, 1934 CONTROL OF CONTRAST WITH COLOR DEVELOPERS Merrill W. Seymour,

Rochester, N. Y., to Eastman Kodak Company,

Rochester, N. Y., a

corporation of New York No Drawing.

Application October 29, 1931, Serial No. 571,942

6 Claims. 11. 95-88) This invention relates to color photography and more particularly to the development of color images by means of color developers. It

the'color images with such color developers.

It is understood that the kind of color developers which I have in mind are those which develop a silver image associated with a color image. Such developers and processes in which they are used are well known and still others have recently "been disclosed in my co-pending applications, Serial No. 536,659 filed May H, 1931,-

No. 555,748 filed August 7, 1931 and No. 55Q,346- filed August 25, 1931 1,897,866 of .Feb. 14, 1933. These developers comprise reducing agents, which, of themselves,

yield colored insoluble oxidation products when they act upon exposed silver bromide, and also developers containing a"'couplin'g agent that combines with the oxidation product of the reducing agent to form a colored insoluble substance.

when a color developer isused to produce a color image forming a part of a two or three color subtractive picture, it is often necessary to control the contrast or gamma An obvious method is the one used in the development of ordinary s' ver images, namely, the alteration of the time of development or the dilution of the developing solution. This method, however, results in a variation of the degree of development of the exposed silver bromide. Under certain conditions, however, particularly in 'color processes, it is necessary to develop the exposed silver bromide to completion, or to a 'degreefixed by the nature of the process, and to fix or control independently the contrast or gamma of the color image.

One means of accomplishing this result is partially to develop the latent image in a color developer, and to complete development ina nonstaining developer, or vice versa. This method, however, involves development in two separate solutions.

The non-staining developer may be of any familiar type such as any mula: known as M-Q. color developers and of may be used and to which the present invention is applicable are to be found'in the applications referred to above. It is whenever in these or analogous processes, a color forming. developer is described, them maybe used a two step developer.

development as a whole relates specifically to the control of contrast of.-

matured into Patent No.

of the color image.

of the common -for- Numerous examples of processes in which they to be understood that must sometimes be carried to completion. The first step would, however, be controlled in duration. If the first step is in a color forming developer, it would be carried to such a point that the desired color contrast is obtained. The second step would then be carried to completion in a non-staining developer to, assure that all exposed grains were developed. If the first step is in the non-staining developer, the'development would be carried only to such a point that when a following color forming development is carried to completion, the desired col'or rendering will be obtained.

It is, of course, impossible to lay down any specification as to relative times of the two steps since these will be determined by the particular emulsion and the factors of the developers that affect contrast and'development.

This method may be utilized to control the color rendering, color intensit' color ratio or balance and contrast.

What I claim is:

1. The method of developing a color photograph which comprises completely developing a latent image in a silver halide layer, such de- "yelopment being partially in a color developer a separate non-staining deof the color development be- .to yield a desired color ren- -veloper and partiallyin a separate non-staining developer, the extent of development in each developer being controlled in accordance with the desired color rendering and the second development being carried to completion.

4. The method of developing a color photograph which comprises iirst partially developing developing a color photoa latent image in a silver halide'layer in a nonstaining developer and then developing it to, completion in a color developer, the extent of the first development being so controlled in duration that the color development will give a desired color rendering.

5. The method of making a color record that comprises completely developing a latent image in a silver halide layer, such development being partially in a developer that yields a colored image comprising silver and a colored compound and partially in a separate non-staining developer yielding only a silver image, the extent of development in the first named developer be- MERRIIL W. SEYMOUR.

ing controlled in duration to produce a desired color rendering. 

